The present invention concerns devices for reducing pollutants discharged by an internal combustion engine. More specifically, the invention relates to such devices adaptable to diesel engines which trap particles and vapor carried by the exhaust gas discharged from the engine.
It is recognized that the production of noxious oxides of nitrogen (NOx) which pollute the atmosphere are undesirable. Steps are therefore typically taken to eliminate, or at least minimize, the formation of NOx constituents in the exhaust gas products of an internal combustion engine. The presence of NOx in the exhaust gas of internal combustion engines is generally understood to depend, in large part, on the temperature of combustion within the cylinders of the engine. In connection with controlling the emissions of such unwanted exhaust gas constituents from internal combustion engines, it is widely known to recirculate a portion of the exhaust gas back to the air intake portion of the engine (so-called exhaust gas recirculation or EGR). Since the recirculated exhaust gas effectively reduces the oxygen concentration of the combustion air, the flame temperature at combustion is correspondingly reduced, and since NOx production rate is exponentially related to flame temperature, such exhaust gas recirculation (EGR) has the effect of reducing the emission of NOx.
It is further known to adapt the engine with electronic sensors to evaluate and control various operational parameters of the engine. One example includes providing a differential pressure transducer across an orifice to measure mass flow rate of the exhaust gas. Using this mass flow rate measurements of the exhaust gas, exhaust gas recirculation may be controlled to optimize engine performance and decrease emission levels. These sensors are typically placed in direct contact with the intake or exhaust gas which are often hostile to the electronic sensor itself. For example, the differential pressure sensor may be placed within the exhaust system that is in direct contact with debris laden exhaust gas.
Debris mixed with the exhaust gas includes particulate emissions can cause extensive damage to engines turbochargers or superchargers. Particulate debris is abrasive and enters the engine oil causing undue wear on the piston rings, valves, and other parts of the engine. A common form of particulate matter is xe2x80x9csootxe2x80x9d which is a sticky substance that can lead to carbon build-up on surfaces exposed to the soot. The soot is particularly damaging to electronic sensors such as temperature and pressure sensors. Soot build-up on the sensor causes a degradation in sensor accuracy and in some instances permanent damage.
FIG. 1 depicts a typical engine and EGR system 10 including known components for actively controlling the mass flow of the recirculated exhaust gas. An internal combustion engine 12 includes an air intake manifold 14 attached to the engine 12 and coupled to the various cylinders 16 of the engine, typically through valves (not shown). Intake manifold 14 receives intake ambient air via conduit 18. An exhaust gas manifold 20 is attached to the engine 12 and coupled to the exhaust gas ports of the various combustion cylinders typically through valves (not shown). The exhaust manifold 20 exhaust combustion gas to the atmosphere via exhaust gas conduit 22. The engine 12 typically includes a fan 24 which is driven by the rotary motion of the engine to cool engine coolant fluid flowing through a radiator (not shown) positioned proximate the fan 24.
An exhaust gas recirculation line 26 is connected at one end 28 to the exhaust gas conduit 22, and at its opposite end 30 to an EGR cooler 32. The cooler 32 reduces the temperature of the exhaust gas in anticipation of re-entering the inlet air stream of conduit 18. An EGR flow control valve 34 is connected at one end 36 thereof to EGR cooler 32 via conduit 38, and at an opposite end 40 thereof to exhaust manifold 20 via conduit 42. The valve 40 is controllable to open or close the EGR path in response to engine performance requirements.
An air intake system (not shown) provides a supply of fresh intake air through a filter (not shown) to compressor 44 of a turbocharger 46. A first portion of the exhaust gas discharged from exhaust manifold 20 of engine 12 is supplied to intake conduit 18 through exhaust gas recirculating line 26 to combine with fresh air driven by the turbocharger compressor. A second portion of the exhaust gas flows through turbine 48 of turbocharger 46 to rotate compressor 44. As a result, intake air exiting from compressor 44 of turbocharger 46 is compressed and heated. The compressed intake air preferably flows through an intake air cooler 50 to reduce the air temperature to a level for optimum combustion in the engine cylinders. Intake air cooler 50 may be an air-to-air type heat exchanger, however, other types of diesel engine coolers or heat exchangers may be satisfactorily used. In operation, the EGR flow control valve 34 is controlled by an engine control module 52 (ECM) in response to differential pressure sensed through a pressure sensor 54 providing a pressure signal to the ECM 52, via signal path 56. The ECM 52 uses the differential pressure to calculate the mass flow rate of recirculated exhaust gas through valve 34. In response to the pressure signal, ECM 52 provides a corresponding control signal to EGR valve 34, through control circuit 58. Therefore, the EGR valve 34 is controlled via the ECM 52 to divert any desired amount of exhaust gas directly from the exhaust gas recirculation line 26 to intake conduit 18.
In one attempt to decrease particulate carried by the exhaust gas, devices referred to as xe2x80x9cbaghousesxe2x80x9d have been employed to filter solid material carried by the exhaust gas. The baghouses can be provided with a fiber bag to capture debris with little on no exhaust gas backpressure. However, once a substantial amount of particulate is captured by the bag the device would lead to a detrimental increase in exhaust gas backpressure. This backpressure can result in a build up of debris within the exhaust system causing poor engine performance and ultimately failure of the engine.
Other known devices which decrease particulate emissions carried by the exhaust gas include regeneration devices which burn away the accumulation of debris. U.S. Pat. No. 5,390,492 to Levendis discloses a regeneration device for use with a filter assembly to decrease the particulate emission in the system. The regeneration device includes a collection chamber fitted with an electric powered incinerator to burn away material accumulating in the collection chamber. Unfortunately, the device is complicated and not a viable alternative for internal combustion engines utilizing after market equipment to decrease exhaust particulate. Furthermore, regeneration devices tend to be expensive to implement and are susceptible to malfunction.
U.S. Pat. No. 5,458,664 issued to Ishii et al. discloses a particle trap provided with a metallic mesh filter, the particle trap is placed directly in the exhaust gas line and is sized to avoid significant exhaust gas backpressure. However, the filter inherently accumulates debris and decreases the flow area, and consequently, an unwarranted back pressure develops. The backpressure in the exhaust line causes degradation of engine power and permanent engine damage, after a period of time.
What is therefore needed is a device for trapping debris in the form of exhaust gas particulate and vapor to protect equipment downstream and at the same time cause only insignificant restriction of exhaust gas from the engine. Moreover, a device that is inexpensive to manufacture and includes widespread adaptability to virtually all sizes and types of engines is desirable. Preferably, such a device should be serviceable rather than warranting periodic device replacement.
These unmet needs are addressed by the exhaust gas recirculation system of the present invention. In one aspect of the invention, an exhaust gas recirculation system for an internal combustion engine includes intake and exhaust manifolds to respectively receive ambient air and expel exhaust gas. A recirculation line fluidly connects the exhaust and intake manifolds. An exhaust gas recirculation valve is included in the recirculation line and is controlled to distribute exhaust gas into the intake manifold. A particle and/or vapor trap is arranged to receive all of the exhaust gas from the exhaust manifold and includes a particle collection chamber therein. A stagnation region is provided within the particle trap configured so that all the exhaust gas passing through the trap is directed toward the stagnation region therein and at least a portion of debris carried with the exhaust gas is retained within the particle collection chamber.
The present invention further provides a particle trap for an exhaust gas recirculation control system for use with an internal combustion engine including a housing having at least one inlet and at least one outlet. A flow deflector is included in the housing and is arranged to deflect a flow of exhaust gas discharged from the inlet. A stagnation region is provided within the housing and is in fluid communication with the inlet and is placed in relation to the flow deflector to receive all exhaust gas from the inlet. The stagnation region is in fluid communication with the outlet through an exhaust gas portal wherein substantially all of the flow of exhaust gas is directed toward the stagnation chamber to urge separation and collection of debris entrained in the exhaust gas.
In one aspect of the invention, the flow deflector is in fluid communication with an inlet cavity. The inlet cavity is in fluid communication with the stagnation region through an exhaust gas acceleration region to urge the flow of exhaust gas toward the stagnation chamber.
It is one object of the present invention to provide an exhaust gas recirculation system that receives substantially all of the exhaust gas expelled from the internal combustion engine such that debris carried by the exhaust gas is trapped and prevented from accumulating on operational sensors and the EGR valve.
Another object of the present invention is to provide a particle trap for an internal combustion engine which traps substantially all the debris, in the form of soot and vapor, expelled from the engine without a significant backpressure caused by the particle trap.
Yet another object is to provide a particle trap which may be readily integrated into new and existing internal combustion engines alike and one which is serviceable rather than requiring periodic replacement. Also, a particle trap which does not require electrical connection to operate and one which is inexpensive and not complicated to manufacture is desirous.
These and other objects, advantages and features are accomplished according to the systems and methods of the present invention, as described herein with reference to the accompanying figures.